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The European Space Agency (ESA) completed one of the biggest space feats in years on Wednesday when it landed a robot on a comet speeding between Jupiter and Mars at nearly 40,000 mph.

The Rosetta spacecraft dropped the refrigerator-sized Philae lander onto comet 67P/Churyumov-Gerasimenko, which is made up of plunging cliffs and rocky terrain.

It's the first time mankind has ever attached a robot to a comet. The chance of success was just 70 percent.

An up-close look at comet 67P on Nov. 11, 2014, the day before the big landing.

Why This Mission Is a Really Big Deal

Comets are like time capsules packed into rocky nuggets that speed around our solar system. Scientists believe they hold clues to the story of our solar system because they may have formed about 4.6 billion years ago — around the same time as Jupiter, Saturn, Uranus and Neptune.

It's possible that these planets and comets are made up of the same chunks of ice and dust that the Sun spit out during its birth.

Many scientists even think comets were a crucial part of Earth's formation because they crashed into our planet during its formative years, spewing organic molecules that were essential to life, something that the Rosetta team hopes to uncover on this mission.

Philae's view

The lander took this photo of the comet just before touchdown. As the image shows, Philae was right on target.

HOW THEY DID IT

Target Spot

On Nov. 12, the Rosetta spacecraft landed Philae on the surface of comet 67P.

It was no small feat: The comet is traveling nearly 40,000 mph, and Rosetta, which is speeding alongside, dropped the lander on a site known as "Agilkia," located on the smaller "head" lobe of the comet, which is kind of shaped like a duck.

Just days before the landing, Rosetta's navigation camera took a photo of the landing site. The image below was captured from about 19 miles away.

The landing site, which is a little less than one square mile, is made up of large, jagged boulders, making the landing very risky.

What Happened

Rosetta deployed Philae around very early on Wednesday from about 14 miles away from the center of the comet. Once released, Philae was on its own — all ESA could do from there was watch the descent, which took about seven hours.

Another thing that made this mission even harder? The time difference. Because the event took place about millions of kilometers from Earth, it took ESA controllers 28 minutes and 20 seconds to communicate with Rosetta each way.

As Philae slowly made its journey without any propulsion or guidance, the orbiter continued on its trip away from the comet's nucleus, looking back to monitor the lander's progress.

When Philae reached the surface, its speed was about the same pace as walking. That may sound like a gentle landing, but the comet's gravity is about 100,000 times weaker than Earth's gravity, so ESA had to prevent the lander from essentially bouncing back into space. In order to do this Philae deployed an ice screw from each foot into the surface of the comet. Meanwhile, the lander fired two harpoons to lock itself into place.

Initially, the Rosetta team thought the first deployment of the harpoon was a success, but they later learned it didn't work, so they tried a second time.

ESA/Rosetta/Philae/CIVA

Comet 67P as seen from a distance as Rosetta made its approach on Aug. 2, 2014.

6 BIZARRE FACTS ABOUT THE MISSION

1. GoT's Lord Baelish and Rosetta have something in common.

To promote the Rosetta mission ESA made a fantastical, highly produced short film starring Aidan Gillen, the actor who plays Littlefinger in Game of Thrones. The video, called "Ambition," features a post-apocalyptic planet in which humans have magical powers to create solar systems. ESA said the film is "a larger tribute to how contemporary space exploration is crucial to searching for clues to our own origins."

2. Scientists have an inside joke about a rubber duck.

Scientists have jokingly dubbed Comet 67P/Churyumov-Gerasimenko a “rubber duck” in space due to its irregular shape. Others say it would be more accurately described as a “black swan” due to the deep black color caused by its non-reflective surface. Explanations for the comet’s unique shape vary. Some experts believe it is a true “contact binary,” meaning it is made of two objects that melded together after impact. Alternatively, it could have been molded into its irregular form through impact with other objects.

3. Rosetta's comet stinks — literally.

According to researchers at the University of Bern in Switzerland, the cloud of gas surrounding comet 67P smells like rotten eggs, horse urine, methanol and formaldehyde — odors not uncommon for comets like this. As the comet nears the sun, it will release more gases and smell even worse, the Los Angeles Times reported.

4. Of course William Shatner is involved.

It only makes sense, right? In a video released by ESA, actor William Shatner sent well wishes to the Rosetta Mission. "I am so excited and I wish you such good luck," the Star Trek actor said.

5. The comet is singing.

As the Rosetta spacecraft neared comet 67P, researchers were taken by surprise by a low, songlike hum coming from the comet. It turns out, the “singing” is caused by the release of electrically charged particles, a phenomenon scientists still don't fully understand.

ESA has uploaded the comet’s song on a Soundcloud page using the hashtag #cometlanding for your listening pleasure.

6. Rosetta has been taking selfies.

The Comet Infrared and Visible Analyser (CIVA) on Philae is comprised of seven cameras that are capable of taking 360 degree photos of the comet's landscape once the spacecraft lands. CIVA can also take selfies from its place on the Rosetta spacecraft. This image shows the side of the Rosetta spacecraft with the comet in the background.

ESA/Rosetta/Philae/CIVA

TIMELINE OF THE 10-YEAR JOURNEY

THE COMET

Nov. 6, 2014

The Agilkia landing site is seen on this image of comet 67P.

Nov. 4, 2014

The center of the comet, as seen from about 20 miles away.

Oct. 26, 2014

An up-close look at the comet 67P, taken from 6 miles away.

Sept. 10, 2014

A wide-angle image of 67P, showing jets of cometary activity along almost the entire body of the comet.

Sept. 12, 2014

An up-close shot of Philae's backup landing site.

Aug. 3, 2014

Comet 67P as seen from 186 miles away.

The Comet's Size (in Earthling Terms)

Another photo of comet 67P, which Rosetta took just one day before the Philae landing.

6 QUESTIONS, ANSWERED

What took Rosetta so long to get to the comet?

Rosetta had quite a ways to travel for its date with fate. Comet 67P hangs out somewhere between the orbits of Jupiter and Earth at a range of about 186 million to 800 million kilometers from the Sun.

Since no rocket launcher was able to get Rosetta all the way out there, rocket engineers had to use the gravity of Mars and Earth to essentially sling it into orbit. The total trip spanned 6.4 billion kilometers (nearly 4 billion miles) and took 10 years.

Why this comet?

The selection of 67P/Churyumov-Gerasimenko is a classic case of right place, right time.

For starters, it comes around somewhat frequently. Comet 67P has a pretty short orbital period, meaning scientists were able to predict when it was coming and where they could find it when it was time to launch Rosetta. Other factors included technical risk to the spacecraft—like how much dust the comet produces—and funding.

How much did the mission cost?

The total mission cost of Rosetta, according to ESA, is close to 1.4 billion euros ($1.7 billion), with the total cost of Philae amounting to 220 million euros. This includes the costs of a one-year launch delay. This also includes the entire 20-year span of the mission, from the start of planning in 1996 to the end of the mission next year. According to NASA, the total cost of the mission was about $900 million before the one-year launch delay, which occurred in 2003 after problems arose with the Ariane rocket. The delay added another $70 to $80 million to the total mission cost.

What if we fail?

If Rosetta somehow fails—say, crash lands or gets pulverized by dust—and the mission is a bust, it's not actually a total loss.

The orbiter will still undergo nearly a dozen experiments and observations that will allow scientists to map the nucleus and gain a better understanding into the processes that occur near, on and inside a comet as it is warmed by the Sun.

What is the different between comets and asteroids?

Both asteroids and comets are thought to be ancient remnants of the early years of our solar system, more than 4 billion years ago.

Comets can be several miles wide, and contain ice, rock, and organic compounds. According to NASA, most comets may be traced to a region beyond the orbits of the outermost planets.

Comets undergo major changes when they move into areas with more intense sunlight, within the inner solar system. When this occurs, the different types of ice in the inner sections of the comet can vaporize and fall away, while gas wraps around the center of the comet, creating a fragile atmosphere known as a coma.

The dust that had been in the nucleus of the comet forms a tail that is sometimes visible from Earth, and can stretch for a thousand miles or longer. Comets striking the Earth are thought to have helped kick-start crucial processes that led to life on the planet, from the early oceans to the atmosphere. Comets may have brought the first carbon-based molecules to Earth, a key building block to life.

In other words, you may owe your life, at least in part, to ancient comets.

In contrast to comets, most asteroids lack the complex inner structure that comets have. Instead, they're comprised of rocks or metals, and are much smaller than comets. Asteroids can be between the size of small boulders to objects that are hundreds of miles wide.

Some asteroids may be the leftovers of past comets, after all their ice and organic compounds have escaped into space. Rather than originating outside the orbits of the outermost planets, asteroids are thought to be part of the Main Asteroid Belt, with orbits between Mars and Jupiter.

Some asteroids have orbits that come very close to Earth, and evidence of near-misses with asteroids that could survive a trip through Earth's atmosphere has increased in recent years. However, most asteroids that encounter Earth's atmosphere burn up as they descend, and break up into smaller debris, known as meteorites.

How long will Rosetta operate?

The first phase of the mission will last two-and-a-half days. The lander, Philae, will be on primary battery power and taking a handful of scientific measurements. After that, the lander will transition into phase two, which will use solar power for approximately three months to take a second set of observations.

Scientists aren't really sure how long the lander will last, though, and chalk up the timeframe's factors to unpredictable "solar illumination conditions"—and dust.

Rosetta, meanwhile, will keep on keepin' on. Its near-term goal is to stick with the comet until it passes the sun in August 2015.

Long term? It's up in the air. (Well, in this case, it's up in the vacuum of space.)

INSIDE PHILAE

Rosetta's Philae lander is about the size of a refrigerator with 10 key instruments:

APXS: Alpha Proton X-ray Spectrometer

This instrument studies the chemical composition of the comet at the landing landing site. It will also look at how the comet changes as it gets closer to the Sun.

CIVA: Comet Nucleus Infrared and Visible Analyzer

Six cameras that will take panoramic pictures of the comet's surface.

CONSERT: Comet Nucleus Sounding Experiment by Radiowave Transmission

This tool will study the internal structure of the comet nucleus with Rosetta orbiter.

COSAC: The Cometary Sampling and Composition

An experiment that will detect and identify complex organic molecules.

PTOLEMY

This instrument will use the MODULUS protocol (Methods of Determining and Understanding Light elements from Unequivocal Stable isotope compositions) to understand the geochemistry of light elements, such as hydrogen, carbon, nitrogen and oxygen.

MUPUS: Multi-Purpose Sensors for Surface and Sub-Surface Science

This will be used to study the comet surface and sub-surface's properties.

ROLIS: Rosetta Lander Imaging System

This instrument will provide us with the first close-up images of the landing site.

ROMAP: Rosetta Lander Magnetometer and Plasma Monitor

ESA will use this to observe the comet's magnetic field and plasma environment.

SD2: Sampling, drilling and distribution subsystem

This will be used for drilling up to 23 centimeters deep. It will also deliver material to onboard instruments for analysis.

SESAME: Surface Electric Sounding and Acoustic Monitoring Experiment

ESA will use this to probe the mechanical and electrical parameters of the comet.